In electrical parts such as motor cores and transformer cores, efforts have been made to increase density and to make the design more compact. There has been a demand for parts that provide more precise control at low power. As a result, there has been on-going development in soft magnetic materials used in these electrical parts, especially in materials with superior magnetic properties in medium- and high-frequency ranges.
For example, Japanese Laid-Open Patent Publication Number 2002-246219 presents a dust core and method for making the same that allows magnetic properties to be maintained even under high-temperature environments (Patent Document 1). In the method for making a dust core described in Patent Document 1, a predetermined amount of polyphenylene sulfide (PPS resin) is mixed with an atomized iron powder coated with phosphoric acid, and this is then compressed. The obtained shape body is heated in the open air for 1 hour at 320 deg C., and then for 1 hour at 240 deg C. The structure is then cooled to form the dust core.
[Patent Document 1] Japanese Laid-Open Patent Publication Number 2002-246219